The present invention relates to an antihypertensive method comprising administering to a patient a pharmaceutical agent containing lithospermlc acid B and the pharmaceutically acceptable salt thereof as the effective ingredients. Lithospermic acid B and the pharmaceutically acceptable salt thereof are contained in a Chinese and Japanese traditional medicine, Salvia miltiorrhiza Bunge. As is described in Japanese Patent Laid-open Publication No. Hei 1-268682 (1989) (the applicant and the inventors are the same as in the present invention, respectively), the present inventors have extracted lithospermic acid B in water From the root of Salvia miltiorrhiza Bunge in water and isolated by chromatography on a column filled with packing agents, a porous gel carrier and Sephadex(trade mark; manufactured by Pharmacia, Co. Ltd.; the same shall apply hereinbelow). Then, the inventors have accomplished the analysis of the steric chemical structure. Simultaneously, the inventors have examined whether or not lithospermlc acid B has all action to improve a renal function, and have provided a method for producing a renal function-improving pharmaceutical agent to decrease uremigenic substances in a rat with an adenine induced renal impairment as well as a method for producing the salt of lithospermic acid B.
It has been known conventionally that Salvia miltiorrhiza Bunge has vasodilating and antihypertensive actions. The present inventors have made further investigations to elucidate what actions as a pharmaceutical agent for use in the disease of cardiovascular system may be exhibited with lithospermic acid B per se, as an isolated substance from Salvia miltiorrhiza Bunge, and with the pharmaceutically acceptable salt thereof. Consequently, the inventors have firstly found that the salt of lithospermlc acid B has a distinctive antihypertensive action. Thus, the present invention has been achieved.